/**
 * @description 根据经纬度计算距离，参数分别为第一点的纬度，经度；第二点的纬度，经度
 */
export default function(lat1, lng1, lat2, lng2) {
	let EARTH_RADIUS = 6378.137; // 地球半径
	let radLat1 = (lat1 * Math.PI) / 180.0; //lat1 * Math.PI / 180.0=>弧度计算
	let radLat2 = (lat2 * Math.PI) / 180.0;
	let a = radLat1 - radLat2;
	let b = (lng1 * Math.PI) / 180.0 - (lng2 * Math.PI) / 180.0;
	let s =
		2 *
		Math.asin(
			Math.sqrt(Math.pow(Math.sin(a / 2), 2) + Math.cos(radLat1) * Math.cos(radLat2) * Math.pow(Math.sin(b / 2), 2))
		);
	s = s * EARTH_RADIUS;
	s = Math.round(s * 10000) / 10000; // 输出为公里
	return {
		m: s * 1000,
		km: Number(s.toFixed(2))
	};
}